Sorry for the late response. You're right, to get a read lock you need to use the locked method and put your code in a callback. Inside a read lock, you can use [url=https://www.mediamonkey.com/docs/apinew/classes/Native.SharedList.html#getValue]getValue[/url] and [url=https://www.mediamonkey.com/docs/apinew/classes/Native.SharedList.html#getFastObject]getFastObject[/url]. getFastObject is faster than getValue when you call it multiple times because it doesn't require extra memory allocation, but it reuses the same item in memory so you can't use it when storing track data for later use.

[url=https://www.mediamonkey.com/docs/apinew/classes/Native.SharedList.html#beginUpdate]beginUpdate[/url] and [url=https://www.mediamonkey.com/docs/apinew/classes/Native.SharedList.html#endUpdate ]endUpdate[/url] are unrelated to read/write locking and are instead used if you plan to modify the list, where a single change event is fired once after you're done, instead of firing a change event any time you make a modification. Haven't checked the source code but I think you should do beginUpdate and endUpdate inside of a modifyAsync callback. If you want to update *track data* like a song title you don't need to use modifyAsync, but if you want to add/remove songs from the list, modify the selected index, etc., use modifyAsync.

The new (WIP) documentation pages aren't super clear on those distinctions, and I can't find the SharedList blurb from the old documentation page (https://www.mediamonkey.com/docs/api/classes/SharedList.html) so I'll try and make sure that's added.

let list = uitools.getSelectedTracklist();
await list.whenLoaded();
list.locked(() => {
   for(let i=0; i<list.count; i++) {
    console.log('track', track);
   }
});

I figured out the problem (Or how to get around).
I was treating the list of tracks returned from [b]uitools.getSelectedTracklist[/b] as a [b]Tracklist[/b] object and only looking at [url=https://www.mediamonkey.com/docs/api/classes/Tracklist.html]those docs[/url].

The methods I found there are what I described above, which didn't work for me.
But in seeing that [b]Tracklist[/b] extends [b]SharedList[/b], I had a look at [url=https://www.mediamonkey.com/docs/api/classes/SharedList.html]those docs[/url] and found an example approach using it's methods.

So now my code is something like:
[code]
let list = uitools.getSelectedTracklist();
await list.whenLoaded();
list.locked(() => {
for(let i=0; i<list.count; i++) {
console.log('track', track);
}
});
[/code]

let list = uitools.getSelectedTracklist();
await list.whenLoaded();
list.beginUpdate();
for(let i=0; i<list.count; i++) {
    console.log('track', track);
}
list.endUpdate();

let list = uitools.getSelectedTracklist();
await list.whenLoaded();
list.forEach(track => {
    console.log('track', track);
});

I've attempted to edit access tracks from the now playing list in two ways.
The first is what the documentation seemed to encourage as far as I could tell.
However, even though I'm using the commands to lock the list, I still get [b]Uncaught (in promise) Error: Read lock not acquired![/b]. (I also get it if I don't lock the list).

[code]
let list = uitools.getSelectedTracklist();
await list.whenLoaded();
list.beginUpdate();
for(let i=0; i<list.count; i++) {
console.log('track', track);
}
list.endUpdate();
[/code]

However, with the second method, found on the forums, it works fine (Even when I edit the extended meta tags).

[code]
let list = uitools.getSelectedTracklist();
await list.whenLoaded();
list.forEach(track => {
console.log('track', track);
});
[/code]


This confuses me. What's different about the two approaches? Aren't I still getting a track object either way?
Also, when does one need to lock the list if not in this case?

Thanks,
Dale.